1. Field of the Invention
The present invention relates to a mobile communication system. More particularly, the present invention relates to a method and an apparatus for paging a terminated call in a mobile communication system.
2. Description of the Related Art
Mobile communication systems have been developed to provide communication while allowing for the mobility of users. Mobile communication systems have reached a stage where a high speed data communication service can be provided, as well as voice communication, because of the strength and rapid development of technologies.
Currently, a standardization shift from a 3rd Generation Partnership Project (3GPP) system to a Long Term Evolution (LTE) system is progressing in the direction of next generation mobile communication systems. The LTE system is a technology which implements high speed packet based communication having a transmission rate of a maximum of 100 Mbps faster than a data transmission rate of the conventional 3GPP system.
The LTE network is a packet based network, which is differentiated from Global System for Mobile communications (GSM)/General Packet Radio Service (GPRS) and Wideband Code Division Multiple Access (WCDMA) networks which provide all of packet/circuit services. Additionally, the LTE network simultaneously provides an Internet Protocol (IP) based service as the packet network and supports a circuit based service through interworking with a conventional generation mobile communication network. For example, technology supporting a voice call service in the LTE network includes Circuit Switched Fallback (CSFB), which disconnects LTE and uses a 3G (circuit network) when a terminal located in the LTE network receives a voice call, and Voice Over LTE (VoLTE) in which a terminal converts a user's voice to a data packet and transmits the converted data packet on the LTE network.
The LTE network divides its own service area into a plurality of areas according to a predetermined rule, allocates distinguishable identifiers to the divided areas, and registers and manages terminals which subscribe to the LTE network within each of the divided areas. Through the divided areas, the network initiates a terminated call service by broadcasting (referred to as “paging”) information regarding whether a packet/circuit terminated call service for a particular subscriber terminal is generated to an area where the corresponding terminal is registered, or by informing the corresponding terminal of the fact in a one-to-one correspondence (referred to as “Circuit Switched (CS) notification”).
The LTE network provides Tracking Area Identity (TAI) list information through which a paging message is broadcasted from the LTE network for the corresponding terminal through an ATTACH-ACCEPT message during an ATTACH procedure where the target terminal accesses the LTE network. The TAI list includes at least one area which is referred to as a Tracking Area (TA) and an identifier of an individual TA is referred to as a “Tracking Area Identity (TAI)”.
When the terminal having successfully accessed the network moves from a currently accessed cell to a cell included in another TAI list, the terminal performs an area update through a Tracking Area Updating (TAU) procedure. The TAI list includes a plurality of TAIs. When the terminal moves within the corresponding TAI list, a separate TAU procedure is not performed. However, when a CS-domain terminated call for the target terminal operating in an idle mode is generated, the LTE network informs the corresponding target terminal of generation of the terminated call service by broadcasting the paging message to the area included in the previously informed TAI list.
When the generation of the CS-domain terminated call for the particular terminal is recognized, the LTE network broadcasts the paging message to the area included in the TAI list of the corresponding target terminal. When the corresponding target terminal moves to an area which is not included in the current TAI list, the paging message cannot be received.
Further, after the corresponding target terminal has completed the TAU procedure in an area which the target terminal newly enters and has received a new TAI list, most of the LTE networks do not re-transmit the paging message which had been transmitted to the old TAI list areas to the newly updated TAI list areas for the corresponding target terminal. Accordingly, a problem of stopping the terminated call service occurs.
Therefore, a need exists for a method and an apparatus for paging a terminated call in a mobile communication system.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present invention.